The recent incidents of anthrax-laced letters being transported through the United States Postal Service (USPS) facilities by unsuspecting mail handlers to unsuspecting recipients has alarmed the nation and the world. Currently, the tainted letters are discovered after the recipient accepts delivery or by alert postal employees noticing white powder that could be anthrax on mail parcels, sorting and distribution equipment, or themselves. There appear to be no current security devices or procedures that are available to intercept such letters at the earliest source of introduction into the USPS system, for example at the depository or drop boxes.
Many depository boxes already exist both in the US and around the world and they vary in form from stand-alone to built-in structures. Such depositories also take the form of ATM banking machines and less common, but still known, automated teller postal machines. Such postal machines are described in U.S. Pat. Nos. 4,900,905; 5,369,258; 4,940,887; 5,025,3386; 5,273,183 and 5,313,404.
Therefore, it would be desirable to have an apparatus which would provide the detection of particulate contamination in depository boxes of various types and applications.